I need help about programming

Hello Guys

my name is Azeem and i am working on php / mysql

i want to showing ids from table and make code this

<?php
$sql="select * from $table where cat_id=$cat_id";
$result=mysql_query($sql);
while($rs=mysql_fetch_array($result))
{
echo $id=$rs['id'].",";
?>

and showing result like this
1,2,3,4,

but i want result like this 1,2,3,4
means not include coma(,) in last digit

anyone tell me that how can i do this ?
please help me
i am thank to yours

 

Change it to something like

<?php
$i = 0;
$sql="select * from $table where cat_id=$cat_id";
$result=mysql_query($sql);
while($rs=mysql_fetch_array($result))
{
if ($i<>0) echo ',';
echo $id=$rs['id'];
$i++;
}
?>

Code (PHP):